THE TREATMENT 





OF FINE GOLD 


IN THE 


SANDS OF SNAKE RIVER, IDAHO. 


BY 


T. EGLESTON, Ph. D., 

!i > 

NEW YORK CITY. 


A Parer read before the American Institute of Mining Engineers 
at the Ottawa Meeting, October, 1889 . 



AUTHOR’S EDITION. 
1890 . 





























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[TRANSACTIONS OF THE AMERICAN INSTITUTE OF MINING ENGINEERS.] 





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THE TBEATMENT OF FINE GOLD IN THE SANDS OF 

SNAKE RIVER, IDAHO. 


BY T. EGLESTON, PH.D., NEW YORK CITY. 

(Ottawa Meeting, October, 1889.) 

The sands of Snake River, Idaho, have long been known to con¬ 
tain gold. They were worked by some of the first prospectors who 
came to Idaho, and on the banks still stand the ruins of camps 
abandoned for years. There are almost always prospectors search¬ 
ing for gold during the season of low water, and it is not an infre¬ 
quent thing to find a miner of the old type actually panning the 
sand, or the prospect-hole which he has just left. There is more or 
less mystery about these miners and their methods of finding the 
spots where they work. They are always subjects of much spec¬ 
ulation to the ordinary traveller. The rich discoveries are, for the best 
of reasons, concealed until the claims can be taken up. It is difficult 
to find a place where there are no prospects, but the “ colors” are so 
very fine that they do not offer much inducement to enterprise. 
The California miner usually values a color at from 5 to 10 cents, 
often the latter; while on Snake River it would take 100 colors, or 
even more, to make that amount. 

There is not much difficulty in panning out the heavier pieces of 
this gravel, so that those which remain have not over half the diam¬ 
eter of a pin’s head. Below this size the separation is extremely diffi¬ 
cult, as the flakes are very thin. The heavier pieces of the basalt, 
the black sand and fine gold remain persistently together; and, after 
the iron has been separated by a magnet, there still remainA a 
material which appears grayish to the eye, has about the same grav¬ 
ity as the light particles of gold, and cannot be removed with an 
electro-magnet run by a very strong battery. After the heavy black 
sand has been separated by the magnet, the fine particles of gold float, 
while the gray sand sinks; so that I had the greatest difficulty in 
concentrating half a liter of material, taken up from under the head of 
the burlap sluice, into a bulk of 15 by 4 millimeters. A large part 
of the concentrated gold floats; and when, after much trouble, the sur¬ 
faces are wetted and the gold is got under the water on to the top of 



2 TREATMENT OF GOLD IN THE SANDS OF SNAKE RIVER. 

the sand, the first wave from the other side of the pan over the sand 
floats the gold again. 

The minerals contained in the fine sand are quartz, chalcedony, 
semi-opal, zircon, topaz and magnetite. I have not been able to 
distinguish any trace of pyrite, and have only occasionally seen 
small grains of periodote. These minerals are sometimes ground 
and broken, and sometimes are small detached crystals, which can, 
however, be seen only with high powers. The gold itself is in 
flattened forms. Almost every piece is convex and shows surfaces 
which are bright and more or less mammilated, having the appear¬ 
ance of having been acted upon by some reagent. They are quite 
similar to the artificial nuggets which I described some years since.* 

It is a question of interest how this gold got into the sands. The 
most probable answer seems, at first sight, to be that it came from 
the abrasion of the rocks. This leads to the further question, Why 
is it, then, so very much finer than gold-sands ordinarily are? I do 
not pretend to be able to answer these questions decisively now, but 
hope to do so at sqme future time. The object of this paper is 
rather to describe the method in use for catching a part of the gold. 

Snake River, during the course of nearly 100 miles, which I have 
studied, runs through a columnar basalt. This rock covers the 
plains, where the surface of the flow is covered with great nodules 
from 15 to 40 feet in diameter, and from 10 to 20 feet high, which 
have a radiated and at the same time a columnar structure. The 
erosion and destruction of this rock has formed the sands of the 
great Idaho desert. The rock is much fissured and is covered only 
to a slight depth with sand. It is generally compact, but the surface 
of the ground is covered in some places with small pieces so full of 
bubble holes that they appear like scoria. All such pieces have a 
more or less large coating of silica on them. It is in this rock that 
the Lost River disappears, to come out again, as is generally be¬ 
lieved, in one of the numerous large springs which flow from the 
north side of the bluff below Shoshone Falls. 

The Oregon Short Line railroad crosses Snake River at American 
Falls station, where the river is 1500 feet.wide and descends 50 feet 
in several falls 10 or 15 feet high between bluffs 30 to 60 feet high. 
It runs West in this way a little over 100 miles, the bluffs on both 
sides of the river gradually growing deeper, until at what is known 
as Twin Falls the river suddenly falls 175 feet, leaving the bluffs 


* Trans., ix, p. 633. 





l, m*' 





TREATMENT OF GOLD IN THE SANDS OF SNAKE RIVER. 3 


*>()() feet high. In the course of the next 3 rriifes it forms Shoshone 
Falls, where the river first narrows to 750 feet in width and then 
takes a jump, first of 75 feet and then, within a few yards, of 210 
feet, leaving the bluffs at the foot of the Falls 1200 feet high on 
both sides of' the canon and the river 1000 feet wide. The top of the 
bluffs is a very hard compact basalt, with occasional small nodules 
of chalcedony, but only in a single place, just above the Twin 
Lakes, below Shoshone Falls, did I see in this top rock any large 
holes, and nowhere any appearance of weathering or decomposition 
in the rock itself in place. The rock is in many places coated 
with a white covering of silica, formed by the evaporation of 
the water percolating through or collected on the surface. These 
coatings sometimes take fantastic shapes, as in the case of the Devil’s 
Spade, about a mile above Shoshone Falls, where what appears to 
be a painting in white of a gardener’s spade can be seen in a niche 
just below the top of the bluff. Notwithstanding this deposition of 
silica, the rock shows to the eye no trace of decomposition. I was 
told that iron pyrites is found in nodules in the upper part of the 
bluffs; but I did not see, in the course of more than a week that I 
spent on the river, a single piece of iron pyrites, however small, 
though I looked carefully for it. Below the great Shoshone Falls, 
on the level of the river, the rock is porphyritic, light gray in color, 
and much more felspathic and friable than the basalt above, and 
thoroughly rotten from decomposition. About 100 feet from the 
foot of the falls it is so worn away that I crawled through 
apertures in the decomposed rock for 25 or 30 feet, at a dis¬ 
tance of about 10 feet above the water, the outside of the rock 
still being intact. This decomposition is much like that which 
occurs in the sand-rock of the Kentucky River near Jackson, Ky. 
It is Dot an uncommon thing in the various side-canons which lead 
into the main canon of the river to find that the bottom-rock has 
been so much decomposed, by the absorption of its alkalies, or so 
much washed out, that pieces of the overhanging hard rock, 50 to 
75 feet in length and 8 to 10 feet in width, have dropped down, re¬ 
taining their vertical position, leaving a chasm 2 or 3 feet wide 
between them and the main rock. Striking examples of this occur 
in the side canon near the Twin Falls and below the Great Falls. 

This decomposition of the underlying rock has taken place on a 
very large scale, and is particularly visible just above and for a con¬ 
siderable distance below the main falls, so that the surface for 500 
feet from the main cliff’ is broken up into what appears at first sight 


4 TREATMENT OF GOLD IN THE SANDS OF SNAKE RIVER. 

to be small terraces, which are difficult of access. From the top of 
the cliffs this sinking of the rocks gives an appearance, on a very 
small scale, quite similar to the grand cafion of the Colorado river, 
as seen about 75 miles from Flagstaff, Arizona, when the same phe¬ 
nomena takes place on a different rock, on a scale probably larger 
than anywhere else in the world. The water of the river is cool, 
and slightly alkaline to the taste. The soil is full of alkali, which 
is undoubtedly one of the results of the decomposition of the rock- 
It is also probably one of the sources of the solution of the gold, 
and its subsequent deposition in the sands of the high banks as well 
as the deposition of the silica minerals formed by evaporation. 

It is a fact well known to those who chlorinate pyrites concen¬ 
trates, that the gold they contain is in all degrees of fineness; 
that, in some cases, it is extremely difficult to attack the gold; and 
that, in other cases, the loss in roasting is enormous, on account of 
the very large surface, as compared to the weight, of the gold par¬ 
ticles. It is known that the gold is much finer in some pyrites 
than in others, and I supposed at first that this might account per¬ 
fectly for the condition of the gold in these sands. The microscopic 
examination, however, does not justify the conclusion that the gold 
has come exclusively from the decomposition of pyrites; since 
in no case have I been able to find any gold that was coated, or the 
surface of which was not just as bright as if it had been for a 
long time exposed to chemicals. That small quantities of gold are 
contained in solution in the waters flowing through these rocks 
seems to be probable. The experiments that I have been able to 
make in the laboratory tend to confirm this opinion. 

Snake River, below Shoshone Falls, runs for 18 miles through 
basalt, the height of the bluff varying from 1200 feet at the falls to 
about 500 feet at the end of that distance. It then commences to 
widen out gradually, the talus of sand increasing little by little in 
height until at last the outlines of the rock only, come up at the top 
of the bluff. These finally disappear; and what was a talus be¬ 
comes sand-hills on the south side, and, on the north, more or 
less irregular sand-bottoms, with cliffs of basalt varying in height, 
but generally not more than 30 to 40 feet high, so that in several 
places roads have been constructed in the side canons from both sides 
down on to the bottoms. On the top of the bluff there is no water. 
The rock is columnar and very much fissured. It dips South, so 
that there are no springs on the South side of the river, but all 
along the North side at intervals of three or four miles great springs 


TREATMENT OF GOLD IN THE SANDS OF SNAKE RIVER. 5 


gush out, which form at once considerable streams, issuing directly 
from the rock. 

The river bottom-lands widen from nothing to about half a mile. 
They rise above low-water mark as much as 30 to 40 feet. Where 
it is possible to get water to them, either from the springs on the 
North side or by flumes taking water high up the river on either 
side, the sands, after the alkali is washed out of them, make excel¬ 
lent soil, and in both ways some beautiful ranches have been made. 

The sand in the river contains some gold, not in large quantity 
anywhere. It is so very fine that it is difficult to collect it without 
special apparatus. The gold value of these sands is estimated at 
about five cents to the cubic yard, which includes top soil and bot¬ 
tom gravel as well. The pay-streak is richer than this, but in the 
working it is impossible to make any separation. 

The pay-streaks, after prospecting, are worked on both sides of 
the river. There are a number of these placer-workings about 50 
miles below Shoshone Falls, which have been operated fora number 
of years by a method but little known. One of these, known as 
Hunt’s placer-claim, at Salmon Falls, which is 17 miles across the 
desert from Bliss station on the Oregon Short Line railroad, I had 
occasion to visit in the summer of 1889. 

The method of excavating the sands is simple. It consists in 
bringing a ditch into the pay-dirt, and making the ditch itself do 
almost all the work of excavation. The fall of the water breaks the 
ground down, and sufficient grade is given to carry it to the machines. 
The best grade for the water-ditch has been found to be 4 inches in 
12 feet. Ditches with earthen banks, and flumes, sometimes partly in 
earth, and at others wholly on tressels, are used. When the ground- 
sluice is not over 36 inches wide, gravel runs easily on a 4-inch grade. 
The long flumes have a grade of 3J inches in 12 feet. The ground- 
sluice is made so as to work gradually back, cutting itself out by the 
fall of the water. The top soil is broken back by the pit-man with a 
steel bar, and the lumps are broken up with a light pick. The pay- 
gravel varies from 10 to 25 feet in thickness, and has to be washed in 
benches, taking from 5 to 8 feet fora bench. No ditch is required in 
the gravelly places. The stream is directed around the bank by the 
pit-man, who uses “ shear boards”, 14 inches wide and 2 inches thick, 
with round sticks 1 foot long and 2 inches in diameter, run through 
them as handles. These are so placed as to direct the water against the 
bank, to undermine it slowly, so that the sands cave, but not so rap¬ 
idly as to impede the course of the water. These planks require the 


6 TREATMENT OF GOLD IN THE SANDS OF SNAKE RIVER. 

constant attention, in the day time, of one man in the pit, who in ten 
hours will bar down ground enough to keep the machine working for 
twenty-four hours. The skill of the pit-man consists in so barring 
his gravel and arranging his shear-boards that the pit will take care 
of itself at night. The current must be strong enough to carry all 
that falls into the sluice leading to the machine. Occasionally, the 
ground-sluice is dammed by the gravel in the night, and cuts a 
channel in such a way as to make it impossible to reach certain 
blocks of ground. This is not, however, a serious inconvenience; 
since the ground has to be broken in benches, and the spot so left is 
taken in, in working the bench below. 

The stream carrying the broken-up gravel runs through sluices, 
in general not more than 24 inches wide. But, from about 8 feet 
before it reaches the first iron plate of the machine, the sluice is en¬ 
larged, so that where it meets the plate, it is 4 feet wide. The ma¬ 
chine consists of a board-sluice Figs 1 and 2, lined with perforated 
sheet-iron plates, 3 by 4 feet in size, which are called “ grizzlies.” 
Below them, on both sides, is an inclined sluice, leading to an under¬ 
current, which discharges into sluices covered with burlap, called 
“ sack-boxes.” The width of the machine is constant; but the length 
varies with the fineness of the gold to be caught. At Hunt’s claim 
there are three—one 24, one 30, and one 36 feet long. The flume 
that carries the gravel is 1 foot lower than the top of the “ grizzly.” 
The sand accumulates here and makes a pavement, and prevents the 
wearing of the bottom. In some of the small machines this sluice is 
paved for some distance with wooden blocks placed on end ; but all of 
them have blank plates for the length of one plate, at least, set almost 
without grade; and these have been found to wear best, as the water 
builds its own grade from the sluice to the machine. The blank 
plate is 4 feet long. It is made, like the other plates, of steel or 
coke iron, of an inch thick. The grizzly-plates are perforated 
with conical holes, J an inch between centers, which are on 
the top and f on the bottom, to prevent the holes from clogging. 
These plates are 3 feet long and 4 feet wide. The sides of the sluice 
are made of boards, 1 inch thick and 12 inches wide, except just 
over the undercurrent, where they are 2 feet wide. The grade of 
the “grizzlies” varies from \ to f of an inch, according to the size 
of the gravel. The coarser it is, the more grade is required. In 
setting up the machine, a frame is first built, and on this the grizzly 
is placed loose, so that the grade can be changed if necessary by 
wedges placed underneath it. Ordinarily, J an inch to the loot is 


TREATMENT OF GOLD IN THE SANDS OF SNAKE RIVER. 7 


found to be the best grade. When the grade is determined, the grizzly 
is wedged firmly to its place. At the end the grizzly discharges the 


Fig. 1.—Plan. 



k 

< 3' 5 

^ 3' ' 

A' f 3 ' > 

PERFORATED iron 

< 2' 1 

PLATES 

Lr 0 ' „ 

y ’ 



(, Holes ; 

'a in. in dian 

1 

leter at bottom Tapering 

to %2 in - a 

Top, 1 in. a 

1 

oart.) 

1 


a,, it 

=f>JXi i-yJI n 




Fig. 2. 

Section through A B, Fig. 1. 



Plan and Section of Apparatus for Saving Fine Gold. 


material too large to go through the holes into the tail sluice, which 
must have sufficient grade to carry off all the tails. Below the 






























































































































































8 TREATMENT OF GOLD IN THE SANDS OF SNAKE RIVER. 

grizzly the sides incline both ways towards the center at the rate of 2 
to 3 inches, or more, to the foot, and end in an undercurrent 
called a “ sand-tank,” which is 4 feet wide. This has a grade of 1J 
inches to the foot, towards each side. It is generally placed imme¬ 
diately under the center line in the middle of the machine, but its ex¬ 
act position depends on the lay of the ground. In its center is a sump, 
4 inches lower than the lead-boxes, so as to distribute the water 
equally to the burlap-sluices on each side of the machine. These are 
4 feet wide, incline J to f of an inch to the foot, and' are arranged 
according to the length of the grizzly. For the 36-foot grizzly there 
are twelve of them, six on a side; for the 30-foot, there are ten, five 
on a side ; for the 24-foot, there usually are only six, three on a side. 
Four would work better. The grade of the lead-boxes is J to 1 inch 
to the foot. The lead-sluices are arranged, so that the back one carries 
the gravel to the sluice furthest away from the machine. They are 
10 inches wide. In order to distribute the sand evenly in the width 
of the sluice, there are four divisions at their head, which vary in 
length so as to distribute the current equally. At their upper end 
there is a movable grating made of strips of wood, set inclined, to 
keep out any floating matter which may accidentally get in. and to 
further distribute the stream. The sluice-boxes are 3 feet wide, and 
24, 30 and 36 feet long; made of thin boards placed end to end. 
The sides are 6 inches high and are nailed to the sides of the bottom 
boards. They have a grade of J to J of an inch to the foot. If the 
material treated is all sand, which is the usual case, the grade is J ; 
if gravel and sand together, j. These burlap-sluices connect with the 
tail-sluice by a sluice at their end, at right angles to the main sluice, 
which is 3 feet wide and has a grade of J an inch to the foot, over 
which the burlap-sluices project 6 inches, and which projects 2 feet 
beyond them. These sluices, like the grizzly, are set on a frame, so 
that the grade can be changed by wedging, and when once deter¬ 
mined on, can be set firmly in place. As the tail-sluices are on both 
sides of the machine, they discharge in front of the grizzly with 
sufficient force to move all the tails down the main tail-sluice. 

At the head of the burlap-sluice, just beyond the wooden gratings, 
which regulate the flow of the gravel, is a cross-cleat, under which 
an iron plate, 1 foot wide and as long as the width of the sluice is 
fitted. This is made of old grizzly iron. It is held down at the 
side by a cleat, under which it slips. 

The sluice is covered with burlap 40 inches wide. It has been 
found by experience that 7 ounces to the yard is the best burlap to 
use. Heavier and lighter have been used, but are not found to 


TREATMENT OF GOLD IN THE SANDS OF SNAKE RIVER. 9 


answer so well. The lead-sluices have a grade of 1 inch to the 
foot; when the plate is put on them, there is a slight drop; and 
here there is always gold to be seen at the clean-up. Each of the 
lead-sluices is so arranged that it can be cut off separately. This is 
done by a gate of wood wrapped with burlap to make it quite tight 
and, in order to further keep out the water, the burlap, which is to 
go on to the sluice after the clean-up, is thrust into the lead behind 
the gate, which prevents the passage of water and at the same time 
wets the burlap, so as to fit it to be spread out on the sluice. These 
gate-wrappings, as soon as the clean-up is finished, are hung up on 
each side of the grizzly, so as to be ready for use at the next clean-up. 
The burlaps on the sluices are held down by cleats of wood, kept in 
place by wooden eccentrics, screwed to the side, so that when they 
are turned down, they hold the cleat in place. These cleats are 1J 
by 1 inch and are cut from a 1-inch board. After six years’ use some 
of them are so worn that they have to be turned up on their angles 
to meet the eccentrics. In the 24-inch sluice there are six of these 
on each side. 

To make a clean-up, the man in the pit comes down to the ma¬ 
chine with the superintendent, and the water is turned off from each 
of the sluices, one at a time, commencing always with the outside 
sluice. The assistant has a piece of flat rubber set in a handle. He 
knocks down the eccentrics on both sides of the sluice to be cleaned 
up, with the handle, so as to loosen the cleats. These are then taken 
out, washed in the next sluice and placed crosswise over it, to be at 
hand when wanted. The superintendent takes out the iron plate at 
the top and carefully scrapes off the sands and gold, washing the 
plate in the next sluice. The assistant takes the burlap from the bot¬ 
tom, brings it up to the center of the sluice, and commences to push 
with his rubber the material collected underneath the burlap on the 
bottom from the lower end to the middle of the sluice. The super¬ 
intendent carries the top of the burlap to the middle, folds it to 18 
inches and the width of the sluice, then doubles it over towards the 
side of the sluice, presses it flat with his feet, and places it in one of 
the boxes. There are two of these boxes for each sluice. They 
are 18 inches long, 13 inches wide, and 7J inches deep, and are lined 
with tin. The woodwork of the boxes is only knocked together, 
but with constant use they last four years. When the tin com¬ 
mences to rust through, so that they leak, the boxes are used exclu¬ 
sively for the burlaps. The tight boxes are always used for the 
sand. While the superintendent is arranging the blankets, the 


10 TREATMENT OF GOLD IN THE SANDS OF SNAKE RIVER. 

assistant goes to the top and pushes the sand down to the middle, 
to be put into the other box. When the sluice is clean, the fresh- 
wetted burlap is taken out of the lead-sluice, the upper end being 
held by the superintendent and the lower end by the assistant, and 
stretched with both hands over the sluice, leaving the upper end of 
the burlap to project over the upper end of the sluice. The burlap 
is shoved under the cross-cleat by the iron plate, which is cut oft* at 
the corners to prevent cutting the burlap; this goes under the cleat 
and is held fast, leaving about 2 inches of the burlap projecting 
over the top of the plate. The side-cleats are now taken from the 
adjoining sluice and put in, commencing at the top. On their hands 
and knees the two men go from the top to the bottom, pressing the 
cloth in place, spreading the burlap so that it comes up to the sides 
of the cleats and sometimes over the top, according as it stretches. 
They then turn down the eccentrics, put in the grating, and turn on 
the water. This work, in a single sluice, takes five minutes. The 
next sluice is treated in the same way, and so on until the clean¬ 
up is completed. They are careful to spread the burlap tight and 
smooth; for, if it is wrinkled or bulges, sand collects under it and 
less gold is caught. If they are properly put down, only two or 
three pans of sand will be thus collected which, at the head of the 
sluice, contains considerable visible gold. Most of the gold, how¬ 
ever, is caught in the burlaps. 

The burlaps are cut so as to cover the whole length of the sluice 
and lap over the lower end; but they wear, and after some use grow 
short, so that they are generally eighteen inches to two feet shorter 
than the sluice. The lead-sluices at the head of the burlap-sluice, 
which distribute the stream, are keyed in and are kept together by 
diagonal strips. The grating is put in loose, 6 or 8 inches from the 
slats. 

Nothing but burlap has been found to answer for this work. 
Ducking was used at one time, but it did not catch the gold so well 
and rotted too fast. The burlaps stre used until they go to pieces 
from rotting. They usually last two months. When worn out, 
they are used around the gate. When they can no longer be used, 
they are dried and burned, and the ashes are panned. In order to 
prevent the closing of the pores by vegetable matter, the burlaps 
must be spread out in the sun to dry thoroughly after each clean-up, 
to destroy the plant-life before they can be used again. They last 
longest in summer. In the winter they are apt to tear from freez¬ 
ing at the sides. The whole work of the three machines is done by 
F I 


TREATMENT OF GOLD IN THE SANDS OF SNAKE RF VER. 11 


five men,—one man in each pit; the helper, who does other work; 
and the superintendent, who, with the pit-men, makes the clean-up 
and “ rocks ” the dirt. 

Over the 24-foot machine, 200 to 250 inches of water are con¬ 
stantly run in X4 hours: on the 30-foot, 350; and on the 36-f'oot, 
400 inches. The work done on each machine averages about a cubic 
yard of gravel for each miner’s inch of water used. The essential 
requisite is to secure a good dump ; unless this is done, the tail-sluices 
will soon be filled up. Usually, on Snake river the spring freshets 
wash the tail-sluices out; but for two or three years, on account of 
the low water in the river, this has not been the case. It is also 
necessary to set the bed-rock sluice in such a way that there will be 
plenty of water the year round. In some places it has been set too 
high, so that when the river is low there is no water to wash with, 
while there is plenty of water in the river. Not only plenty of water, 
but free water is essential to the economical success of this process. 

The boxes from two of the machines which are at a distance, are 
cleaned in a shed near the house, half a mile from the sluices. In 
one which is difficult of access, the rocking is done on the spot. 
The clean-up house is 14 by 12 feet. On the long side against a 
window is the washing-tank. An ordinary gold-sand rocker is 
placed at the end next a window, and the retort-furnace opposite to 
it. The boxes containing the burlaps are piled next the washing- 
tank. The sand in the boxes is piled next to the rocker. The 
washing-tank is 10 feet long, 3 feet wide and 3 feet deep. It has 
a shelf 6 inches wide behind, and one 4 inches wide at an angle of 
forty-five degrees in front. The burlap taken from the box is 
washed several times up and down in the tank, where water is 
constantly running in and out. It is then allowed to fall into the 
tank ; the end being held by the hand, is washed by shaking it on 
to the front ledge, and is then folded backward and forward so as to 
make the folds 1 foot wide. It is then thrown on to the ledge be¬ 
hind. The gold sand from the burlap which remains on the front 
ledge is then washed into the tank, the end of the burlap is brought 
over on to the front ledge, while the rest remains on the opposite 
ledge, and the space between the two parts of the burlap washed 
up and down and again folded on the front ledge. This is repeated 
twice; so that each burlap is washed three times. The ledge is 
washed every time to throw the gold into the water. The washing is 
done at some distance from the discharge-pipe, to avoid the danger 
of the fine gold floating off. The sand collected at the bottom of the 


12 TREATMENT OF GOLD IN THE SANDS OF SNAKE RIVER. 

vat is allowed to settle until the water is almost clear. The water is 
drawn off from above at three plug-holes, at different levels, and the 
sand collected is rocked. The rocker has a plate 60 inches long 
by 24 inches wide. The end and sides are turned up 1 inch, so 
that the inside space on the plate is 22 by 59. The hopper, into 
which the sand is put, is 13 by 15 inches, and 5 inches deep. The 
bottom of the hopper is made of a grizzly plate and the constant 
washing has worn grooves laterally towards the holes. The incli¬ 
nation of the plate is 2f inches in 2 feet, which experience has 
shown to be the best. The plate is copper and not silvered, silver- 
plated plates not having been found to answer. The plate is first 
washed with a swab soaked in potassium cyanide. Then mercury, 
sprinkled half way down through a fine cloth placed over the end of a 
bottle, is wiped over the surface with the cyanide swab. The sand 
is put in at the hopper and the rocker is rocked seventy-eight times 
a minute. What conies off the plate runs into a tail-sluice, and 
carries almost no gold, not more than two dollars to the ton. 
About seven small coal-shovels full are worked in a minute, care 
being taken never to clog the holes. This is all that is done 
with the sand from the boxes. The sand from the tank is 
mixed with cyanide, the proportion being determined by trial, 
and allowed to stand two hours before rocking. The moment 
the rocker is stopped, the end of the amalgamated plate is turned 
up so as to drain to the back, to prevent the loss of mercury and 
amalgam. Each machine is cleaned twice a week. The 24-foot 
treats from 78 to 80 tons per day, and the others correspondingly 
more. -The gold collected by this method is very fine,—much 
finer than any that I have seen, except from some of the Arizona 
placers. 

The machine runs itself, with only one man in the pit. It pays 
to run sand which has from 50 to 85 colors. These machines 
collect from thirty-five to forty dollars a day each. The work 
of the clean-up varies with the size of the machine. With the 
30-f‘oot machine, all the work of cleaning up the sluices, washing 
the burlaps, spreading them out to dry, and rocking, is done in 
six hours. The 36-foot machine takes an hour longer, and the 
24-foot an hour less. 

This method is one of the least expensive of all the devices for 
the treatment of fine gold. It requires but little capital and 
labor, and the returns well repay the men. It requires, however, 
free water. By changing the grade of the machine and sluices, 


TREATMENT OF GOLD IN THE SANDS OF SNAKE RIVER. 13 


and multiplying; the number of burlaps, very close work can be 
done. 

I desire to express my obligations to Mr. J. S. Hunt, the owner 
of this claim, and Mr. C. M. Peters, the superintendent, for the 
assistance they gave me while studying the method on the spot, 
and since my return to the East. 































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